The talents of Willy den Ouden were discovered in 1930, when she was still a junior. She won her first Dutch title the next year, still only aged 13. At the European Championships later that year, she claimed a silver medal in the 100 m freestyle, and helped the Dutch relay team earn a gold medal. A year later, Den Ouden added two Olympic silver medals to her prize cabinet, again in the 100 m freestyle and 4 x 100 m freestyle. In 1933, Den Ouden broke her first World Record, setting a 2:28.6 mark in the 200 m freestyle. She would eventually set 15 World Records, although this included some distances no longer recognized. Her 100 m mark set on 27 February 1936, 1:04.6, would remain a World Record for almost 20 years, as it was only broken by Dawn Fraser on 21 February 1956. Den Ouden was one of the stars of the 1934 European Championships, earning gold in the 100 m freestyle and the 4 x 100 m relay. The 400 m ended in a dead heat with compatriot Rie Mastenbroek. As Den Ouden refused a re-swim to break the tie, she was handed only a silver medal. By the time of Den Ouden’s second Olympics, Berlin 1936, she had been eclipsed by Mastenbroek, who won the 100 m freestyle final while Den Ouden finished fourth. They did combine to earn a gold medal in the relay, however. At her last major event, the 1938 European Championships, Willy den Ouden won her ninth and final international medal: a silver in the relay. Ending her career with five Dutch titles (100 m freestyle, 1931-35), Den Ouden fled abroad at the outbreak of World Ward II. Marrying a Swedish shipping manager, she moved to Saltsjöbaden, but returned to Rotterdam upon their separation. Little is known of her life after that, except that she married (and divorced) twice more, and worked in a fur shop.